A variety of photosensitive compositions containing a photosensitive resin have been proposed for providing a resist used in a semiconductor lithography step or the like, a coating material for providing a substrate with a functional surface, or a similar material (see, for example, Patent Document 1). Such a photosensitive composition preferably contains, as a solvent, water instead of an organic solvent, from the viewpoint of an environmental problem. Therefore, the photosensitive resin is preferably synthesized not in an organic solvent or a water-organic solvent mixture, but in water containing no organic solvent. In the case where a substrate is coated with a photosensitive composition, to thereby provide a medical device, a biochemistry test device, or the like, elution, from a substrate, of a substance which adversely affects a living body or the like must be prevented. In such a case, use of a photosensitive composition containing, as a solvent, water instead of an organic solvent is particularly preferred.
The photosensitive resin may be produced through, for example, incorporating a photosensitive compound into a polymer. Patent Document 1 discloses a photosensitive compound which can be dissolved in water to a certain extent and which can be incorporated into a polymer through synthesis reaction in water. However, in order to produce, for example, a photosensitive resin from a higher concentration aqueous solution of a photosensitive compound, a photosensitive compound having a further high water solubility is desired.
Also preferably, the photosensitive composition has excellent storage stability and can be produced from an inexpensive material. However, the photosensitive composition disclosed in Patent Document 1 has problems in that the storage stability thereof is insufficient and that a photosensitive compound which can provide a synthetic photosensitive resin in water must be obtained from an expensive material.